Biomedical subjects

Masakatsu Ueno

Publications and source records attributed to Masakatsu Ueno.

14 recordsLinked to original sources

PubMed2006

Application of Fokker-Planck-Kramers equation treatment for short-time dynamics of diffusion-controlled reaction in supercritical Lennard-Jones fluids over a wide density range.

The validity of a Fokker-Planck-Kramers equation (FPKE) treatment of the rate of diffusion-controlled reaction at short times [K. Ibuki and M. Ueno, J. Chem. Phys. 119, 7054 (2003)] is tested in a supercritical Lennard-Jones fluid over a wide density range by comparing it with the Langevin dynamics and molecular dynamics simulations and other theories. The density n range studied is 0.323n(c)< or =n< or =2.58n(c) and the temperature 1.52T(c), where n(c) and T(c) are the critical density and temperature, respectively. For the rate of bimolecular reactions, the transition between the collision-limited and diffusion-limited regimes is expected to take place in this density range. The simulations show that the rate constant decays with time extensively at high densities, and that the magnitude of decay decreases gradually with decreasing density. The decay profiles of the rate constants obtained by the simulations are reproduced reasonably well by the FPKE treatment in the whole density range studied if a continuous velocity distribution is used in solving the FPKE approximately. If a discontinuous velocity distribution is used instead of the continuous one, the FPKE treatment leads to a rate constant much larger than the simulation results at medium and low densities. The rate constants calculated from the Smoluchowski-Collins-Kimball (SCK) theory based on the diffusion equation are somewhat smaller than the simulation results in medium and low densities when the intrinsic rate constant is chosen to adjust the steady state rate constant in the low density limit to that derived by the kinetic collision theory. The discrepancy is relatively small, so that the SCK theory provides a useful guideline for a qualitative discussion of the density effect on the rate constant.

Journal Article↗

PubMed2005

Electric conductivities of 1:1 electrolytes in liquid methanol along the liquid-vapor coexistence curve up to the critical temperature. III. Tetraalkylammonium bromides.

The molar conductivities of the dilute solutions of the tetraalkylammonium bromides have been measured in methanol along the liquid-vapor coexistence curve up to about 180 degrees C. The limiting molar conductivities and the molar association constants have been obtained from the analysis of the concentration dependence of the conductivity. On the basis of the present data together with the literature ones, the validity of the Hubbard-Onsager (HO) dielectric friction theory [J. Hubbard, J. Chem. Phys. 68, 1649 (1978)] derived from the continuum model has been examined for the translational friction coefficients of the tetraalkylammonium ions in methanol in the density range of 0.8232 g cm(-3) > or =rho > or =0.5984 g cm(-3) and the temperature range of -15 degrees C < or =t < or =180 degrees C. At high densities and low temperatures, the observed friction coefficients of Me(4)N(+) and Et(4)N(+) are remarkably smaller than the prediction of the HO theory (where Me stands for methyl group and Et for ethyl group); this kind of limitation of the HO theory has not been recognized for smaller ions, and can be attributed to the loosening of the solvent structure closely related to the weak charge effect for the large ions. The negative deviation from the HO theory gradually disappears with decreasing density and increasing temperature, and the friction coefficients of Me(4)N(+) and Et(4)N(+) are explained by the HO theory reasonably well at low densities and high temperatures. For Pr(4)N(+) and Bu(4)N(+) (where Pr stands for propyl group and Bu for butyl group), the experimental friction coefficients lay in the validity range of the HO theory in all the conditions studied here; the breakdown of the continuum theory at low densities and high temperatures has not been observed in this work. The density dependences of the molar association constants of the tetraalkylammonium bromides are qualitatively explained by the Fuoss theory based on the continuum model.

Journal Article↗

PubMed2005

Evaluation of blood flow by color Doppler sonography in free jejunal interposition grafts for cervical esophageal reconstruction.

The failure of the vascular anastmoses is a devastating complication in free jejunum transplantation. We used color Doppler sonography to estimate blood flow in free jejunal grafts in 21 patients who underwent radical pharyngoesophagectomy. Fast Fourier transform (FFT) analysis of blood flow, the pulsatility index (PI) as a measure of peripheral vascular resistance, and thickening of the graft wall were evaluated for predictive value. The arterial wave patterns were classified into three types based on systolic-diastolic differences and magnitude of flow. Type I was physiologic flow, type III overtly pathologic, and type II intermediate. The three patients who required vascular reanastomoses intraoperatively had a type II pattern that degenerated to type III within 15 minutes. The PI increased to 3.5 to 4.5 over 1 hour. In the one patient who required retransplantation, the wave pattern became type III by 18 hours and had disappeared by 24 hours, at which point the PI could not be measured. Jejunal thickening increased from 1.0 mm to 5.0 mm after 24 hours, even in healthy grafts. Monitoring blood flow during the 24 hours after surgery is critical. A type III wave pattern or a PI >2.5 is an indication for reexploration. Doppler sonography offers a noninvasive way to measure blood flow in jejunal grafts semiquantitatively and can predict free jejunal graft failure.

Aged↗

PubMed2004

Electric conductivities of 1:1 electrolytes in liquid methanol along the liquid-vapor coexistence curve up to the critical temperature. II. KBr and KI solutions.

The molar conductivities Lambda of KBr and KI in dilute methanol solutions were measured along the liquid-vapor coexistence curve up to the critical temperature (240 degrees C). The concentration dependence of Lambda in each condition was analyzed by the Fuoss-Chen-Justice equation to obtain the limiting molar conductivities and the molar association constants. Using the present data together with the literature ones, the validity of the Hubbard-Onsager (HO) dielectric friction theory based on the sphere-in-continuum model was examined for the translational friction coefficients zeta of the halide ions (the Cl(-), Br(-), and I(-) ions) in methanol in the density range of 2.989rho(c)> or =rho> or =1.506rho(c), where rho(c)=0.2756 g cm(-3) is the critical density of methanol. For all the halide ions studied, the friction coefficient decreased with decreasing density at rho>2.0rho(c), while the nonviscous contribution Deltazeta/zeta increased; Deltazeta was defined as the difference between zeta and the friction coefficient estimated by the Stokes law. The density dependence of zeta and Deltazeta/zeta were well reproduced by the HO theory at rho>2.0rho(c). The HO theory also explained the ion-size dependence of Deltazeta/zeta which decreased with ion-size at rho>2.0rho(c). At rho<2.0rho(c), on the other hand, the HO theory could not explain the density and the ion-size dependences of zeta and Deltazeta/zeta. These results indicated that the application limit of the HO theory lied about rho=2.0rho(c) which is the same as the application limit observed for the alkali metal ions. The present results were also compared with the results in subcritical aqueous solutions.

Journal Article↗

PubMed2004

Electric conductivities of 1:1 electrolytes in liquid methanol along the liquid-vapor coexistence curve up to the critical temperature. I. NaCl, KCl, and CsCl solutions.

The molar conductivities Lambda of NaCl, KCl, and CsCl in liquid methanol were measured in the concentration range of (0.3-2.0) x 10(-3) mol dm(-3) and the temperature range of 60-240 degrees C along the liquid-vapor coexistence curve. The temperature range corresponds to the solvent density range of (2.78-1.55)rhoc, where rhoc = 0.2756 g cm(-3) is the critical density of methanol. The concentration dependence of Lambda at each temperature and density (pressure) has been analyzed by the Fuoss-Chen-Justice equation to obtain the limiting molar conductivity Lambda0 and the molar association constant KA. For all the electrolytes studied, Lambda0 increased almost linearly with decreasing density at densities above 2.0rhoc, while the opposite tendency was observed at lower densities. The relative contribution of the nonhydrodynamic effect on the translational friction coefficient zeta was estimated in terms of Deltazeta/zeta, where the residual friction coefficient Deltazeta is the difference between zeta and the Stokes friction coefficient zetaS. At densities above 2.0rhoc, Deltazeta/zeta increased with decreasing density though zeta and Deltazeta decrease, and the tendencies are common for all the ions studied. The density dependences of zeta and Deltazeta/zeta were explained well by the Hubbard-Onsager (HO) dielectric friction theory based on the sphere-in-continuum model. At densities below 2.0rhoc, however, the experimental results cannot be explained by the HO theory.

Journal Article↗

PubMed2004

Effect of duodenogastric reflux on N-methyl-N'-nitro-N-nitrosoguanidine-induced glandular stomach tumorigenesis in Helicobacter pylori-infected Mongolian gerbils.

Both Helicobacter pylori (Hp) and bile acids are gastric carcinogens. An experimental model of duodenogastric reflux in Mongolian gerbils was developed and was used to study the effects of Hp infection and duodenogastric reflux on N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced glandular stomach tumorigenesis independently and synergistically. Male Mongolian gerbils underwent both inoculation with Hp, and had duodenogastric reflux (DR) induced, or neither, followed by MNNG administration. Animals were sacrificed at week 40, and histopathological examination of their excised stomachs and serological investigation were performed. Glandular stomach adenocarcinomas were observed in animals that underwent Hp inoculation and/or induction of DR after MNNG administration, and glandular stomach adenomas were found in animals inoculated with Hp after MNNG administration. The incidence of glandular stomach tumors was significantly higher in animals inoculated with Hp after MNNG administration and in animals undergoing combined Hp inoculation, DR induction and MNNG administration than in animals only administered MNNG. These findings indicate that Hp infection has a stronger tumorigenic effect than the exposure to duodenal contents, and duodenal contents may attenuate the effect of Hp on glandular stomach tumorigenesis.

8-Hydroxy-2'-Deoxyguanosine↗

PubMed2003

Esophageal tuberculosis presenting with an appearance similar to that of carcinoma of the esophagus.

A case of esophageal tuberculosis presenting with an appearance similar to that of esophageal cancer is reported. The patient was an 82-year-old man with progressive dysphagia. Barium swallow and esophagoscopy revealed an elevated lesion with deep ulceration in the middle thoracic esophagus. Esophageal carcinoma, in particular, an undermining type of undifferentiated carcinoma, was suspected fluoroscopically and endoscopically. Histological examination of biopsy specimens revealed no malignancy, but there were epithelioid granulomas and a few Langhans' type multinucleated giant cells. Endoscopic ultrasonography clearly demonstrated an extramural lesion with calcification and direct infiltration of enlarged subcarinal lymph nodes into the esophageal wall. Ultrasonographic and histological findings indicated the possibility of esophageal tuberculosis. Although no bacteriological evidence was obtained, a therapeutic trial for tuberculosis, using antituberculous drugs, was started. After 2 weeks, the enlarged subcarinal lymph nodes were markedly reduced in size. The patient's symptoms improved gradually and had disappeared 8 weeks after he started treatment, when tubercle bacilli were isolated from sputum. A connection between the esophageal wall and its adjacent structures was clearly demonstrated by endoscopic ultrasonography. For patients with findings indicative of esophageal tuberculosis on endoscopic ultrasonography, a therapeutic trial for tuberculosis should be considered, even if polymerase chain reaction assay or culture is negative.

Aged↗

PubMed2002

Ambulatory intraesophageal bilirubin monitoring in Japanese patients with gastroesophageal reflux.

BACKGROUND: The role of reflux of duodenal contents in gastroesophageal reflux in Japanese patients, which may be different from that in Western patients, was studied. METHODS: Intraesophageal pH and the bilirubin concentration were monitored, using the Bilitec 2000, in 43 patients with reflux symptoms and 10 normal volunteers. The percentage of the time that spectrophotometric absorbance was 0.15 or more and pH was less than 4.0 was defined as the holding times (HTs) of bilirubin and acid, respectively. Severity of esophagitis was classified using the Savary-Miller (S-M) classification. RESULTS: Esophagitis was present in 37 patients; 5, 10, 13, and 9 patients had S-M grades 1, 2, 3, and 4, respectively. Both HTs in the volunteers were less than 5%. Bilirubin HT was more than 5% in 3 of the 6 patients without esophagitis, but the acid HT was less than 5% in these 6 patients. Acid HT was less than 5% in 4, 2, 2, and 2 patients with S-M grades 1, 2, 3, and 4, respectively. Bilirubin HT was less than 5% in 1 patient with S-M grade 2 esophagitis. Bilirubin HT in patients with S-M grades 3 and 4 esophagitis (50.9 +/- 5.8%) was higher than that in grades 1 and 2 (14.9 +/- 2.9%) (P < 0.0001), but this was not so for acid HT. In 32 patients, bilirubin HT exceeded acid HT. Bilirubin HT did not correlate with acid HT. CONCLUSIONS: Duodenogastroesophageal reflux occurred independently of and exceeded acid reflux. The amount of duodenogastroesophageal reflux correlated with the severity of esophagitis.

Adult↗

PubMed2002

[A case of gastric cancer in the stomach wall used for mediastinal reconstruction after esophagectomy in which surgery was abandoned due to advanced age and complications but TS-1 was useful].

The patient was a 78-year-old man. Gastric cancer, type 3, was diagnosed by endoscopy in the subtotal stomach used for posterior mediastinal reconstruction after resection of thoracic esophageal cancer. Surgery was not considered to be feasible in this case because of cerebral infarction and decreased pulmonary functions; instead, the patient received TS-1 chemotherapy. Drug administration was started at the dose of 100 mg/day, one level lower than the standard dose of TS-1. Reduction in tumor size was noted endoscopically during the first course of treatment. At the end of the 4th course of treatment, the ulcerous lesion was found to have disappeared almost completely, and only mild mural irregularity was noted. The incidence of gastric cancer in the stomach tissue used for mediastinal reconstruction after esophagectomy has been reported to be 0.8%. In many of these cases, the cancer is already advanced at the time of diagnosis, precluding surgical resection. In this situation, chemotherapy with TS-1 is expected to be an effective method of treatment that can be administered at home in elderly patients with a variety of complications.

Aged↗

PubMed2002

[Thoracoscopic esophagectomy].

The current roles of thoracoscopic esophagectomy in the treatment of cancer in Japan are described. Lymphadenectomy of the same quality as open surgery should be performed thoracoscopically to obtain good oncological outcomes. The indications for thoracoscopic esophagectomy are 1) no extensive pleural adhesions; 2) pulmonary function sufficient for single-lung ventilation; and 3) tumor not invading other organs. Hand-assisted or mini-thoracotomy facilitates the dissection of lymph nodes, especially on the left side of the trachea. However, for any type of procedure, a good en-face view is essential for safe and accurate lymphadenectomy. The magnifying effect of video, with the camera in close proximity, is important to maintain a proper dissecting plane. Although sufficient experience is necessary to master the learning curve, lymphadenectomy of the same quality as open surgery can be performed with mini-thoracotomy in a feasible time period. Thoracoscopic esophagectomy contributes to reducing postoperative pain and constrictive pulmonary dysfunction. It may be too soon to assert that the thoracoscopic approach can provide oncological outcomes comparable to those after open surgery because long-term follow up is not yet sufficient. Thoracoscopic esophagectomy, however, has the potential to improve the postoperative quality of life of patients with esophageal cancer.

Esophageal Neoplasms↗

PubMedDate not supplied

Oral fluoropyrimidine anticancer drug TS-1 for gastric cancer patients with peritoneal dissemination.

The survival of gastric cancer patients with peritoneal dissemination is dismal and surgical intervention is rarely indicated. The usefulness of TS-1, a novel oral anticancer drug, composed of tegafur, gimestat and otastat potassium at a molar ratio of 1:0.4:1, and the role of surgical intervention for this condition was studied. Among gastric cancer patients with peritoneal dissemination, 18 treated during September 1999 to March 2001, and 16 before March 1999, were classified into the TS-1 group and control group, respectively, and survival was compared. TS-1 was administered orally twice daily, at a dose of 80 mg/m2/day, for 28 days followed by 14 days without treatment. This cycle was repeated. There was no difference in clinicopathologic factors, including surgical intervention, between the two groups. Eleven patients of the control group had chemotherapy using fluoropyrimidine. Grade 3-4 adverse reactions caused by TS-1 occurred in 1 patient. Survival was better in the TS-1 group than control group (p=0.0008), with median survival of 257 vs. 118 days. The median discharged period of patients of the TS-1 group with a performance status 0-2 on the Zubor scale was 211 days. TS-1 was effective to prolong the survival of gastric cancer patients with peritoneal dissemination. In this series of cases, surgical intervention to establish the route of oral administration was essential for this treatment.

Adenocarcinoma↗

PubMedDate not supplied

Causes of death and pattern of recurrence after esophagectomy and extended lymphadenectomy for squamous cell carcinoma of the thoracic esophagus.

Improved understanding of how esophageal cancer behaves following curative resection, including knowledge of other causes of death, is essential for informed decision making. The medical records of 246 consecutive patients with squamous cell carcinoma of the thoracic esophagus who had undergone esophagectomy and lymphadenectomy of the neck, chest, and abdomen that was deemed macroscopically curative, were reviewed. Patients who had had other malignancies or anticancer treatment were excluded. Median follow-up period was 1289 days (minimum, 730 days). The initial patterns of recurrence were classified as intramediastinal, hematogenous, or lymphatic. Forty-two patients died of a cause other than recurrence. The in-hospital death rate was 3.6%, and 19 patients died of pulmonary disease. Sixteen patients developed a second primary, most of which were in the upper aerodigestive tract; five of those patients died. Ninety-eight patients developed recurrence. Depth of invasion and number of nodal metastases predicted recurrence. The pattern of recurrence was intra-mediastinal, lymphatic, and hematogenous in 11, 21, and 67 patients, respectively. The patients with lymphatic recurrence survived longer than the patients with either of the other types of recurrences. Eighty-three percent of recurrences presented within 24 months. The time-to-recurrence correlated with survival after recurrence. The disease recurred earlier in patients with advanced stage than unadvanced disease at the time of esophagectomy. The time-to-recurrence, and anticancer therapy after the recurrence related to the survival. Meticulous care must be taken to detect hematogenous recurrence as early as possible so that adjuvant therapy may be started. Maintaining a good performance status permits the use of aggressive therapy should there be a recurrence. Pulmonary physiotherapy and treatment of metachronous primary tumors may improve overall survival.

Aged↗

PubMedDate not supplied

The prognostic factors after radical esophagectomy for esophageal cancer with positive preoperative CEA.

BACKGROUND/AIMS: We investigated in this paper the clinicopathological factors that affect the prognosis of esophageal cancer with preoperative positive CEA. METHODOLOGY: Out of 252 patients with thoracic esophageal cancer who received curative resection in our department, we selected 33 cases with esophageal cancer that had positive serum CEA level preoperatively. We analyzed the clinicopathological factors which affect the prognosis in these CEA positive cases. RESULTS: There were no differences in preoperative CEA levels according to the variant clinicopathological factors. The number of lymph nodes metastasis, depth of tumor involvement, lymphatic invasion, and preoperative SCC antigen level were the significant factors influencing survival. But, only preoperative SCC antigen level was independent and a significant prognostic factor on multivariant analysis. CONCLUSIONS: While sensitivities of SCC antigen and CEA are low in esophageal cancer, the cases having positive value in both CEA and SCC antigen preoperatively have high recurrence rates after radical esophagectomy.

Aged↗

PubMedDate not supplied

Surgical repair of esophagobronchial fistula caused by radiation injury.

We present an unusual case of a benign esophagobronchial fistula caused by radiotherapy to treat esophageal carcinoma which was closed successfully. A 62-year-old man with superficial squamous cell carcinoma of the esophagus underwent radiotherapy, including 60 Gy externally and 10 Gy intraluminally from January to March 1995. Esophagography revealed a fistula between the esophagus and left main stem bronchus on January 14, 1996. No residual cancer existed. Neither stenting with a silicone tube nor with a covered flexible metallic stent occluded the fistula. Thoracic esophagectomy, closure of the esophagobronchial fistula using a 2-cm nubbin of esophageal wall, surrounding the orifice of the fistula and antesternal gastric pull-through reconstruction with mediastinal lymphadenectomy were performed. The postoperative course was uneventful and there is no evidence of recurrence of the fistula or the cancer 5 years postoperatively. Radiotherapy may cause esophagobronchial fistula even in cases of superficial esophageal cancer. Bypass surgery should be considered because stenting is not effective for benign fistula without stricture.

Bronchial Fistula↗